Interfitting lock



Jan. 19, 1954 R. A. FARRELL 2,666,567

INTERFITTING LOCK Filed April 10, 1950 2 Sheets-Sheet l INVEN TOR.

ROBERT A. FARRELL R. A. FARRELL INTERFITTING LOCK Jan. 19, 1954 2 Sheets-Sheet 2 Filed April 10, 1950 JNVENTOR.

ROBERT A. FARRELL m1. WW4 W Patented Jan. l9, 1954 'INTERFITTING LocK Robert Farrell, Menasha, I Wis.,. assignor to Marathon Corporation, Rothschild, Wis., a corporation'of Wisconsin Application April 10, 1950, Serial'No. 155,035

3 Claims. (01. 229-45) This invention relates to an improved interfitting lock of the type having a tongue portion and a slit portion for receiving the tongue and o more particularly to an interfitting lock adapted to be engaged automatically on packaging machines.

Paperboard cartons are presently in use for packaging which have a pair of closure flaps which are adapted to be interlocked by means of a locking tongue on one of the flaps and a tongue receiving slit on the other. Means have been provided on packaging machines whereby cartons of this general type are closed automatically by movement of the carton through the machine and the locking flaps are brought into engagement and locked together. In general these devices include means for flexing the flap carrying the slit receive the tongue Ill.

portion of the look so as to open the slit, and

other means for inserting the tongue into the open slit. The flexed portions are then released to complete the locking of the flap. I have found that in. certain types of mechanical devices for accomplishing this result it is extremely important that the slitted flap of the carton flexed'or folded in a predetermined area oralong a predetermined line in order to obtain the proper'reg- 'istration' of the slit and the tongue to effect locking. .7 i

It is an object of this in ention to provide a carton having such an'interfitting lock which will have proper-register between the tongue flap and the slit flap because of the improved'construction of the slit flap. Other objects and advantages of my invention will be apparent from the following description.

Reference is made to the drawings forming a part hereof wherein like numerals are used" to Figure 7 is a view similar to Figure 2 showing another modification of my carton.

A carton blank embodying my invention is shown in Figure 1, wherein by suitable cut and score lines there are provided front panel 2, rear panel 3 and side panels 4. To the side panels are connected closure flaps 5 and to the front and rear panels are connected the locking flaps 6 and 1 along hinge lines 8 and 9 respectively. Locking fiap 6 is provided with a tongue I0, and locking flap 7 is provided with a depressable portion l,l defined by a slit [2 which is adapted to The depressable portion II is preferably a tab or tongue l3 of the same configuration as the tongue l0 formed by a central out M which is parallel to the connecting hinge 9 and two shorter cuts l5 of equal length intersecting the ends of the central out It. Tab [3 is so dimensioned as to permit tongue ID to enter the slit I2. A glue panel I6 is secured to the front panel 2 and when the carton is set up as shown in Figure 2 the glue panel overlies and is glued to the adjacent side panel in the conventional manner.

A novel feature of my lock construction is the provision of score lines 20 in locking flap 1 which are in alinement with the central cut I4 of the slit l2. These score lines form a hinge along which the locking flap vI can be folded or will fold under suitable pressure. It is an important featureof my improved carton and carton lock for 7 reasons which will hereafter become apparent that the hinge in the locking flap l formed by refer to similar parts in each of the figures and wherein: I Figure 1 is a plan view of a blank for a folding carton having my improved interfitting lock.

Figure 2 is a perspective view of a set-up carton made from the blank of Figure 1 showing the locking flaps in unlocked-relation.

Figure 3 is a perspective illustrative viewof a carton having my improved interfitting locking flaps at four different pos'itions when passing the cut I4 and the score lines 29 so divides the entire flap I, that depressable tab [3, and slit [2, are contained in an outer panel 2! formed by such division.

The function of my improved lock will be best illustrated by referenceto Figure 3 wherein is shown a preferred type of mechanism for interfitting the tongue flap 6 with the slit locking flap 1 of my carton merely by moving the cartons through a preferred mechanism for automatically locking said flaps.

Figure4 is a perspective view showing the relationship of the flaps of'the' top of my carton in the position in Figure 3 indicated as 11.

Figure 5 is similar. to Figure 4 only the carton is the position in Figure 3 indicated as III. Figure 6 is a partial mid-sectional view illustrating the action of my improved interfittinglock whenat position III in passing through. thelocking mechanism of. Figure 3.

through the mechanism. In Figure 3 I have shown my carton at four different stages within the locking mechanism designated as I, II, III, and IV to illustrate the various stages of the locking operation. Cartons may be moved through these stages by any suitable conveyor (not shown).

The locking .'mechanism comprises a pair of plows 30 and 3| preferably formed of metal which are shaped to perform the functions hereinafter described. These plows are generally mounted in fixed spaced relation'by supports (not shown). Between these plows is aspear 33 the top surface of which isa single edge 34 formed by the 3 intersection of two sloping surfaces 35 and 36. A guide rod 31 secured to plow 30 is arranged in a cooperating relationship with this spear.

In the operation of this mechanism a carton entering between the plows as at I will have loo'lg ing flaps B and 1 extending upward; The closure flaps will have been moved into closed position by other equipment or by hand. The locking" flaps are engaged by the plows and because 79; their shape the flaps are folded inwardlyialong their hinged connections to the cagtonjbody as the carton moves from position I to position II. In position II (see Figure 4) the locking flap 1 is folded over the spear 33. lihe spear is; ar ranged and positioned that the scorelines 20 are in register with the top edge 34 of the spear;

The outer panel 2! of the locking flap 1 has been ioldedto its position by engagement with guide rod 31 which is shaped for this purpose. Because of the score lines 20 this fold will always take place along this predetermined line and hence the depressable tab l3 and slit l2 forming part of the hinge will be wholly in panel 2 I While vthis operation is taking place with respect to locking flap '1, locking flap ii is folded in wardly by plow 3! along its connecting hinge 8,. At. position II flap 6. has been moved only a short distance; In passing from position II to position III the flap 6 passes guide rod 31 and then plow 3! causes it to be folded over and on top of outer panel 2,! as shown in position III. (See Figure 5.) Because of the location of the seores in the lockingpanel the locking tongue 10 of locking flap 6 will overlie depressible tab !3, When this occurs a portion of the spear i r moved and the lock n ton 19 by the ac ion of the plow 3.! d esses he tab and than. nt s ntt openin termed by the slit 12-, Th s s b st l strated inFis r 6: p or tinned movement of the carton from position III to position IV results in the plows flatteningout both of the flaps with the tongue l0 inserted in rnesm z I is an mpo an eature f the locking o ration .c rrield u by my re erred mecha s h t the lock n fl p .5 i n l ed. o ex xcept about its connecting hinge}! at any time during the operation. This greatly improved the rigid: ity of'the finished lock since flexing of paperboard tends to weaken it, and were both flaps folded or flexed the finished lock would not be as satistab I!) having a length a may swing in the same general arc as tongue l0 and hence may be depressed inwardly leaving an opening at length 2), i. e., the distance from the bottom of tab i3 to slit I2 for the locking tongue to enter. Were i the locking panel of this carton to fold, when passing through the locking mechanism, along some line such as line X-X of Figure 2,, the depressible tab 13 and slit l2 would not lie wholly in the outer panel 2|. Consequently when the panel folda the distance b becomes less than the length a of the tab and the tab 13 cannot be depressed by the locking tongue.

Though in the embodiment described the fold or hinge is in alignment with the central portion M of the slit l2, in Figure 7, I have shown a emb d ment. s r n a l. re p sis except that, seore lines ilfl' are between the slit I2 and the flap hinge 9'. The depressable portion H is still wholly in the outer panel 2| and, therefore, the difliculty described above is avoided.

It is still necessary that the lock be properly dimensioned for any ehosen location of the hinge li b"di 'rnent in order to insure proper re and ement of the parts. The advantage of my carton is that for any particular design} registration is assured, whereas, in prior variations in paper board structure cause the fold to take place along difierent lines in dif er nation ,iro es eqii e e c ac of th loc i g m c n sm. hence he flaps b m ut o regi r. a, Ii assesses no Qthr mo i a i s a d em od ments ofm n e i n wi O u to s skilled in the art and no limitations are intended by the above. descr pt o or a reier ed' bod other han r cont ned, he f lowbn a int rfi t ne lode inte fitting laps i ed ng entirely in a substanwhen, 10 5 1 ne, of said fr 'eirins S id ton ue, 5, ems h h to rovides tab in said flap hav ng t ire pfe d ppo e to the ree and 0f the flap a a nge "in said sl e f a e t n m uu ns w {ther in be e the tab r ed by: said slit and the onne i g n e or 'sai 'fiap f H r e .2 In .a paper art n an htrfit ins ck mbri We in 't fla s n e to said ying ent ly m a substantially J A 11ers re se n in g a tensi e n h other having a slit therein for receiving said tongue, s idslitbsi s sha ed as o rqv de a three s d s tab s id other flap hav n i s f ee and oppos te to th end. oi the sai o her fl and a n ein sai slit-ted nae trans ersely t J n ine score lines al ed wi h a p tion o said. lit. to locate said three sided tab, en tirely within the outer panel of said other flap i rmecl by said hinge.

3:. In a paperboardvcarton an interfitting loci; comprising at. least, two interfitting flaps hinged to said carton and lying entirely in a substan.- tially common plane when locked, one of said flaps presenting an integral tongue and the'other having a slit therein for receiving said tongue, said slit being shaped to provide a tab in said nap having its free end opposite to the free end of the flap, and a *l' irig e in said slitted flap extending transversely thereof between said slit a d t e connecting hinge for sa d fl p. 

